1. Field of the Invention
This invention relates to a circuit board for processing signals input via, for example a connector or a connector terminal; a circuit module device in which the unnecessary radiation which sometimes superposes with input or output signals from the signal terminal provided on the circuit board can be reduced; and a typical electronic device such as video recording device or a video display device.
2. Description of the Related Art
As is well known, conventionally, in order to reduce unnecessary radiation generated from the circuit module, the entire circuit module is covered with a electromagnetic wave shield such as a shield cover and the like, and a connection structure is widely used in which a hole is formed at the portion where the circuit module connects with an external circuit, and connection is done using a connection cable or the like from the hole.
A connection structure is also widely used which connects by exposing the connecting parts such as the connector and the like at the external parts of the shield structure.
It is to be noted that a connecting structure which fixes a connector from the back face of a board onto a board installed at a predetermined position in a shield case, and which is used the connection of the electrode which penetrates the front face of the board with the exterior (example, Jpn. Pat. Appln. KOKAI Publication No. 8-148877) is proposed as an example in which it is possible to shield from electromagnetic waves at a predetermined level, while connecting with signal wires from the exterior.
However, in the connection structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-148877, the circuit portion of the circuit module is not completely shielded, and in order to shield the circuit portion, it is necessary to expose the connector portion at the exterior portion of the shield case, and this causes the problem of increased size of the board.
Furthermore, in this connection structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-148877, an opening portion is necessary for connection with the external circuit, and there is the problem that there is unnecessary electromagnetic wave leakage from this opening portion.